PDCD1 and neoplasm: With the application of immune checkpoint blockers (ICBs), scientists have come to realize that the immune activation generated by targeting programmed cell death 1 (PD-1) combined with PDL1and PDL2 [6], or cytotoxic T-lymphocyte associated protein 4 (CTLA-4) combined with CD80 and CD86 [7], is not enough to control tumor progression.